PRISM :: Browsing by Author "Johansen, Craig"

Browsing by Author "Johansen, Craig"

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Open Access
A Detailed Chemical Kinetics Mechanism for Biogas and Syngas Combustion
(2016) Lee, Hsu Chew; Mohamad, Abdulmajeed; Jiang, Lei-Yong; Gollahalli, Subramanyam; Mahinpey, Nader; Johansen, Craig; Du, Ke
The interests in alternative renewable fuels such as syngas and biogas have intensified the search for an accurate chemical kinetics model to describe the combustion of syngas and biogas fuels. Unfortunately, a generally accepted mechanism for the fuels of interest remains elusive. Therefore, this thesis is aimed at developing the most up-to-date chemistry model for syngas and biogas combustion. Based on comprehensive comparison between several notable mechanisms available in the literature, the NUIG2013 mechanism [1] was found to have the closest agreement with the experimental data for H2 –CO–CH4 –CO2 fuel mixtures diluted with N2 and H2O. However, the NUIG2013 mechanism failed to predict accurately the ignition delay time at several experimental conditions and the NUIG2013 consists of too many irrelevant species and reactions for syngas and biogas combustion purpose. Therefore, sensitivity analysis were conducted to identify the cause of discrepancies observed between the predicted results and experimental data, and Genetic Algorithm (GA) approach was proposed and validated to optimally extract relevant reactions for H2/CO/CH4/CO2 mixtures from the detailed NUIG2013 chemical kinetics mechanism. Two new rate constants for H+O2(+CO2) = HO2(+CO2) and CH4+OH = CH3+H2O reactions were proposed based on the sensitivity analysis, and it was found that the modified rate constants reconciled the observed discrepancies between the predicted and the measured results. The GA eliminated 1777 insensitive reactions in the NUIG2013 mechanism [1], where the final detailed chemical kinetics model presented in this thesis for biogas/syngas fuel mixtures comprised of 290 reactions and 72 species. The final detailed chemical kinetics model with the incorporation of the two modified rate constants was validated against a large set of experimental data, and excellent agreements were found between the predicted and experimental data. Consequently, the final mechanism presented in this thesis is currently the most up-to-date detailed chemical kinetics mechanism that is suitable for predicting the combustion properties of biogas/syngas accurately.
Open Access
Aerothermodynamic Measurements in Hypersonic Non-Equilibrium Flows
(2022-11-10) McDougall, Connor Charles; Johansen, Craig; Murari, Kartikeya; Morton, Christopher; Ghaemi, Sina; Davidsen, Joern; Bauwens, Luc
High enthalpy arc-jets are unique facilities particularly suited for producing complex flows in the aerospace field, such as the aerothermodynamics of a re-entry vehicle. Arc-jets are often used to evaluate important design factors that include heat shield materials and vehicle design. Characterization of these facilities is important, as studies often aim to match specific in-flight environments during experiments. Due to the complex environment produced by an arc-jet, with effects such as thermodynamic and chemical non-equilibrium occurring in the flow, characterization experiments are significantly more difficult than in conventional blow-down wind tunnels. The current work aims to characterize an arc-jet facility through spatially-resolved measurements of flow unsteadiness, temperature, and velocity. To achieve this goal, a non-intrusive imaging technique called “planar laser-induced fluorescence” was performed in the NASA Langley Hypersonic Materials Environmental Test System arc-jet facility. The experimental data was analysed to produce the quantitative measurements in multiple regions of the flow around a blunt body specimen. A three-temperature low fidelity numerical solver was created to simulate the flow in order to investigate thermal non-equilibrium effects occurring outside the imaging region in the arc-jet nozzle. Unsteadiness in the test section of the arc-jet was minimized by analyzing a subset of data assessing the gas injection configuration. Radial velocity, rotational temperature and translational temperature measurements are provided that can be used to validate future computational studies. The temperature measurements revealed rotational non-equilibrium occurring behind the bow-shock near the specimen surface. Computational results show the facility is capable of producing thermal non-equilibrium flow in the arc-jet nozzle. This work provides the first experimental and computational evidence of thermal trans-rotational non-equilibrium occurring in multiple regions of this arc-jet facility. Significant improvements to the methodology are also identified as recommendations for future arc-jet characterization studies.
Open Access
An Experimental Investigation of Ejector Ramjet Performance at Static Conditions
(2024-09-16) Long, Lisa; Johansen, Craig; Gates, Ian; Bauwens, Luc
The performance of a methane-fueled ejector ramjet (ERJ) equipped with the Atlantis Intake System (AIS) was tested at static conditions. For static tests with no forward velocity, the AIS ERJ successfully entrained and mixed the stagnant surrounding air to create a stoichiometric mixture of 17.2 when the Mach 2 primary jet’s total pressure was 625 ± 25 kPa. Combustion was most stable when the air-fuel mixture was lean. The maximum positive thrust and specific impulse were 22 ± 3 and 189 ± 33 s, respectively, when the primary jet total pressure was 400 kPa. Engine performance was compared to a 1D Ejector Ramjet (1D-ERAM) solver and showed good agreement with a 95% confidence interval during combustion. The solver did not accurately predict the combustion limits of the engine. Additional tests were performed with a nitrogen-diluted fuel jet, which extended the range of conditions for which the ERJ could sustain combustion. The engine demonstrated increased thrust when the primary jet’s total pressure was increased. The inverse Damkohler number was investigated as a tool for predicting engine blowout and provided improved resolution of the engine’s combustion limits, which could be applied to the 1D-ERAM solver
Open Access
Analytical Unsteady Aerodynamic Models for Horizontal Axis Wind Turbines
(2016) Hammam, Mohamed; Wood, David; Crawford, Curran; Morton, Chris; Johansen, Craig; Ware, Antony; Visser, Ken
This thesis describes the development of unsteady aerodynamic models of wind turbines within the framework of blade element momentum theory. The main purpose is to build analytical models, and test them against available wind tunnel and field test data. The unsteady wake is modeled using vortex methods. The analysis covers unsteady loading due to fast pitch change at constant wind speed, and varying wind speed at constant pitch. The analysis can be extended to more complex conditions. The work starts by modeling dynamic inflow effects as an inertia force, with a new developed expression of the apparent mass and rotational inertia of the rotor vortices. Further assumptions lead to a Ricatti differential equation for the axial induction, which has an analytical solution. First, linear pitch changes are investigated, and the unsteady thrust and torque are calculated. The model is shown to be accurate in comparison to the available experiments. The model is then extended to low tip speed ratios in the form of an Abel differential equation, which appeared to be more accurate. However, comparison with measurements has shown that the assumptions leading to the Abel equation model are inconsistent. The unsteady load is characterized by a large overshoot for high pitch rate. To alleviate this an analytical solution of exponential pitch angle is developed. %An analytical model is obtained for the exponential pitch case and validated against experiment. Next, the unsteady load due to varying wind speed at constant pitch is modeled. The dynamic inflow model is extended to include the circulatory effect of the wake. A new unsteady model is developed from first principles. The wake is modeled as an initial vortex cylinder and vortex rings released onto the wake with each revolution of the blades. The circulatory effect is described by a new function. The model is simplified further by approximating the wake effect to get an analytical solution for the case of linearly varying wind speed. The unsteady lift is modeled and combined with the dynamic inflow model to obtain a fully unsteady model in state space form. The different models are validated with experiments, and the unsteady lift effect is found to have importance for short time period transients.
Open Access
Application of simplified numerical and analytical methods for rapid analysis in atmospheric entry vehicle design
(AIAA Conference, 2015) Hinman, William; Johansen, Craig; Wilson, Steven
Selected simplified numerical and analytical methods are applied to flow around hypersonic adiabatic blunt bodies. In particular, selected methods that are well defined in the literature, such as the modified Newton’s method, transformed finite difference grid in the shock layer, and the method of characteristics in the supersonic region, are utilized to solve the flow around an adiabatic circular cylinder at Mach 6. The results are compared to results obtained by numerical simulation of the compressible Navier-Stokes equations. The comparison is used to draw conclusions about the applicability and accuracy of these methods as they apply to low Reynolds number, small radius of curvature bodies such as atmospheric entry vehicles. A minor improvement to the results is proposed by the inclusion of an iterative interaction between the boundary layer displacement thickness, and the external inviscid free-stream.
Open Access
Assessment and Analysis of a Novel Intake for a Ramjet Engine
(2017) Wilson, Steven James; Johansen, Craig; Wood, David; He, Jianxun (Jennifer); Ziadé, Paul
The Atlantis Intake System (AIS) is a novel intake design intended to supply a combustible fuel/air mixture to a ramjet engine without the use of any moving parts. The operation of the AIS is similar to an ejector pump, it operates via the continuous release of a gaseous fuel jet into a system of inlet stages open to the surrounding ambient air. Interactions between the fuel jet, the intake geometry and the surrounding air result in a relatively high velocity, high pressure, and high temperature combustible mixture entering the intake of a ramjet engine coupled with the intake. A control-volume analysis is used to develop a means of predicting the performance of an AIS coupled ramjet engine given a set of input conditions, to better understand the influence of the controlled variables. This control volume (CV) analysis is expanded to include a method for predicting the ratio of air entrained by the AIS based on the characteristics of the fuel inlet jet and the geometry of the AIS. This model is compared to a series of computational fluid dynamic (CFD) simulations, and shows strong agreement in terms of the ratio of air entrained. The potential for the use of the models as a tool for rapid assessment of multiple AIS designs is discussed. An exergetic analysis tool is developed and utilized on the results of the CFD simulations to quantify the dominant sources of exergy destruction. The results are to be used as a guide to better optimize the AIS.
Open Access
B-Spline Based 3D Model Reconstruction and Finite Element Analysis of Human Knee Joint
(2017) Zhu, Di; Li, Leping; Xue, Deyi; Johansen, Craig; Lu, Qingye
Knee joint is the largest diarthrodial joint in the human body, and the normal joint mechanics is essential for our daily life. Finite element analysis provides an efficient tool for studying knee joint mechanical behaviour under different conditions. Due to the complex shapes of the knee joint, it is important to obtain accurate models with realistic geometries prior to FE simulation. A semi-automatic 3D point cloud fitting procedure in MATLAB based on B-Splines that accounts for contact geometries and CAD compatibility was developed in this thesis. The reconstructed model was then used for nonlinear stress-relaxation simulations under ramp compressions, where pore pressure, contact pressure and reaction forces were investigated. The reconstruction procedure has successfully reduced overclosures at contact surfaces, promoted faster convergence and enhanced simulation performances. This study helps further build the bridge between 2D medical images and FE simulations.
Open Access
Characterization of the Effects of Jet Radial Position on Entrainment Ratio in a Subsonic Ejector
(2022-11-16) Mensik, Ryan Michal; Johansen, Craig; Mohamad, Abdulmajeed; Hassanzadeh, Hassan; Martinuzzi, Robert
The work investigated an ejector-based intake, the Atlantis Intake System (AIS), in static conditions. A control volume (CV) analysis was presented and used to estimate the entrainment ratios of the AIS. The CV analysis also estimated momentum loss due to the jet’s interaction with the mixing chamber walls. An experimental campaign was performed to validate the CV analysis. Pressure and entrainment ratios were experimentally determined for an AIS in a concentric alignment. Secondly, entrainment ratios were recorded for changing lateral positions of the primary tube. This work showed that the entrainment ratio was insensitive to lateral displacement within normalized radial position less than 0.60. For normalized radial positions beyond 0.6, a sharp drop in the entrainment ratio occurred. A maximum of 18% loss in entrainment ratio was measured. This work shows that there is a minimal penalty to entrainment ratio for small offsets of the primary jet and has the potential to simplify ejector and AIS design.
Open Access
Chemical Characterization and Source Apportionment of Ambient PM2.5 over Key Emission Regions in China
(2016) Zhou, Jiabin; Du, Ke; Johansen, Craig; Kim, Seonghwan; Song, Hua
A year-round campaign was completed for comprehensive characterization of PM2.5 over four key emission regions in China. The annual average PM2.5 mass concentrations ranged from 60.5 to 148.9 μg m-3. Nine water-soluble ions collectively contributed 33–41% of PM2.5 mass, with three dominant ionic species being SO42-, NO3-, NH4+, and carbonaceous particulate matter contributed 16-23% of the PM2.5 mass. The characteristic chemical species combined with back trajectory analysis indicated that Wuqing site was heavily influenced by air masses originating from Mongolia and North China Plain regions, whereas Deyang site suffered from both local emissions of Sichuan Basin and biomass burning via long-range transport from South Asia. A molecular marker-chemical mass balance (MM-CMB) receptor model revealed that the major primary contributors to PM2.5 OC were vehicle emission, coal combustion, biomass burning, meat cooking and natural gas combustion, which collectively accounted for 84±24% of measured OC. The major contributors to PM2.5 mass were secondary sulfate (26-30%), vehicle emission (12-26%), secondary nitrate (12-23%), coal combustion (6-12%), secondary ammonium (7-9%), biomass burning (4-12%), meat cooking (2-5%), natural gas combustion (1-2%), and other OM (2-13%) on annual average at these sites. This study found the source apportionment has distinct regional and seasonal characteristics. This knowledge is essential for government to make region specific control strategies for fine particles pollution in China.
Open Access
Coherent Dynamics and Energetics in Thin Flat Plate Wakes
(2021-08) Agrey, Kaden; Martinuzzi, Robert; Hu, Yaoping; Johansen, Craig; Wan, Richard; Pieper, Jeff
The dynamics and energetics of two mean two-dimensional wakes behind a flow-normal thin flat plate, induced by inclusion and exclusion of end plates, are studied. Both wakes are characterized by quasi-periodic vortex shedding but differ in mean topology and typical wake characteristics, such as mean base pressure and recirculation length. Energetically optimal proper orthogonal decomposition modes are used to approximate the coherent motion and thus triply decompose the velocity field into a mean, coherent, and residual field. This is utilized to obtain a dynamic characterization of the wakes and to study the large scale coherent structures and their energetic exchanges with other scales of motion. From this, a slow-varying base flow and lateral shear layer flapping are shown to influence the shedding dynamics differently in each wake. These differences in the mean field and coherent dynamics are related to wake turbulence levels and vortex deformation, and thus are at the beginning of the energy cascade and the energy transfer process related to the wake turbulence levels.
Open Access
Combustion in a horizontal channel partially filled with porous media
(Shock Waves, 2008) Johansen, Craig; Ciccarelli, Gaby
Experiments were carried out to investigate the combustion propagation phenomenon in a horizontal channel partially filled with ceramic-oxide spherical beads. A 1.22 m long, 43 mm nominally thick layer of spherical beads is located at the ignition end of a 2.44 m long, 76 mm square channel. Tests were performed with 6.4 and 12.7 mm diameter beads. A flame is ignited at the bead end wall by an automotive spark ignition system. Flame propagation and pressure measurements are obtained via ionization probes and piezoelectric pressure transducers mounted on the top and bottom surfaces of the channel. High-speed schlieren video was used to visualize the structure of the explosion front. Experiments were performed with a 31% nitrogen diluted stoichiometric methane–oxygen mixture at room temperature and at an initial pressure in the range of 15–50 kPa. For initial pressures of 15 and 20 kPa the flame accelerates to a velocity close to the speed of sound in the combustion products. For initial pressure of 30 kPa and higher DDT occurs in the gap above the bead layer. An explosion front propagating at a velocity just under the CJ detonation velocity is detected in the bead layer even though the bead layer pore size is much smaller than the detonation cell size. It is demonstrated that flame propagation within the bead layer is the driving force behind the very rapid flame acceleration observed, however the DDT event occurring in the gap above the bead layer is not affected by the bead layer porosity. Schlieren video indicates that the structure of the explosion front varies across the channel height and with propagation distance down the channel.
Open Access
Computational fluid dynamics study of optimized hypersonic leading edge geometries
(AIAA Conference, 2015) Hinman, William; Schmitt, Simon; Johansen, Craig; Rodi, Patrick
An aerothermal optimization study of two-dimensional hypersonic leading edge geometries has been performed. The accuracy of a simplified model and a reduced order numerical model was assessed through comparison to simulations of the compressible Navier-Stokes equations performed in OpenFOAM. Specifically, the estimated surface pressure, and laminar convective heating distributions have been compared. The simplified model was found to have compromised accuracy in regions of high and low surface curvature. The reduced order numerical model was found to give accurate results with significantly reduced computational cost compared to complete Navier-Stokes simulations. Optimizations were then performed using the simplified analysis technique, and the reduced order numerical model. The performance of the optimized hypersonic leading edge geometries was analyzed using OpenFOAM. The results show that both methods achieve a similar geometric result. However, the quality of the optimization is improved by using the reduced order numerical model. An analysis was performed in the design space immediately surrounding the optimized geometry to assess the impact of small geometric changes on aerothermal performance. The results show that even small changes in leading edge geometry can have a significant influence on aerothermal performance.
Open Access
Computational Modeling of Cascade Effect on Blade Elements with an Airfoil Profile
(2016-02-03) Yan, Haoxuan; Wood, David Howe; Johansen, Craig; Morton, Christopher
The aim of this project is to investigate the effect of cascade on lift and drag coefficients and the angle of attack at which lift to drag ratio is maximized using the method of CFD. The blades of wind turbines are separated by a finite distance in the azimuthal direction. The Blade Element Theory (BET) assumes a blade element to be an airfoil and the blade element is independent to each other; and conducting experiments for low solidity blades is difficult. Thus, CFD would be an appropriate method to investigate how the cascade effect would impact the aerodynamics of wind turbines. The computational results were compared with experimental results (Hoffmann 1996). User Defined Functions (UDF) of transition SST model were also tested in order to find the most optimal correlations. The results show that the lift and drag coefficients are influenced by the solidity and pitch angle.
Open Access
Conceptual design methods for small-scale supersonic uncrewed aerial vehicles
(2021-09-20) Dalman, Benjamin; Johansen, Craig; Ramirez-Serrano, Alex; Starkey, Ryan; Chiba, Kazuhisa; Wood, David
An investigation of conceptual design methods used for small-scale supersonic uncrewed aerial vehicles (SSUAV) was performed to facilitate future SSUAV design work. Verification and validation analyses of the Stanford University Aerospace Vehicle Environment (SUAVE) was conducted for various fidelity aerodynamics, stability, and propulsion modules. A new weights module, tailored for SSUAV concepts, was developed and implemented into SUAVE. The performance of a new SSUAV concept, the University of Calgary multipurpose unmanned fixed-wing advanced supersonic aircraft (MUFASA), was assessed and compared to two existing designs (GOJETT and M2011). Performance metrics of takeoff distance, maximum flight Mach number, and cruise range were used. As each vehicle design is different, a system was setup to compare them across differing scales. A variety of factors related to this scaling system were examined for their influence on vehicle performance metrics, including off-design turbojet performance, available fuel volume, and predicted empty weights. GOJETT was found to be feasible (capable of completing a full supersonic mission) at a wide range of sizes, while MUFASA required an increase from the existing vehicle size to be feasible. The M2011 did not have any feasible sizes under the system used. The smallest feasible SSUAV was found to have a takeoff mass of 13.41kg.
Open Access
Dense particle cloud dispersion by a shock wave
(Shock Waves, 2013) Kellenberger, Mark; Johansen, Craig; Ciccarelli, Gaby; Zhang, Fann
A dense particle flow is generated by the interaction of a shock wave with an initially stationary packed granular bed. High-speed particle dispersion research is motivated by the energy release enhancement of explosives containing solid particles. The initial packed granular bed is produced by compressing loose powder into a wafer with a particle volume fraction of Φ = 0.48. The wafer is positioned inside the shock tube, uniformly filling the entire cross-section. This results in a clean experiment where no flow obstructing support structures are present. Through high-speed shadowgraph imaging and pressure measurements along the length of the channel, detailed information about the particle shock interaction was obtained. Due to the limited strength of the incident shock wave, no transmitted shock wave is produced. The initial “solid-like” response of the particle wafer acceleration forms a series of compression waves that eventually coalesce to form a shock wave. Breakup is initiated along the periphery of the wafer as the result of shear that forms due to the fixed boundary condition. Particle break-up is initiated by local failure sites that result in the formation of particle jets that extend ahead of the accelerating, largely intact, wafer core. In a circular tube the failure sites are uniformly distributed along the wafer circumference. In a square channel, the failure sites, and the subsequent particle jets, initially form at the corners due to the enhanced shear. The wafer breakup subsequently spreads to the edges forming a highly non-uniform particle cloud.
Open Access
Development and characterization of an inexpensive LED-based light source for high-frame-rate schlieren imaging
(AIAA, 2015) Lincoln, Daniel; Murari, Kartkik; Johansen, Craig
This work presents characterization results of a 623 nm light emitting diode (LED) based light source developed for low-cost, high frame rate schlieren imaging. The LED was overdriven up to 20 times the rated current while generating 100 ns pulses at a 1 MHz repetition rate. Circuit response, pulse train characteristics, and temperature effects were observed over a large range of input voltages. Relative brightness data was measured with a photodiode and further examined within a schlieren system. Flow visualization of a decaying Mach 3 shock wave were obtained with the system. The wave was produced in a shock tube facility used for aerodynamic measurements. The effect of the light source on image quality, including motion blur are analyzed. Furthermore, shock velocity measurements obtained from the schlieren images are reported.
Open Access
Development and Characterization of an LED-Based Light Source for High-Speed Schlieren Imaging
(2016-02-03) Lincoln, Daniel; Johansen, Craig; Murari, Kartikeya; De Visscher, Alex; Morton, Chris; Wood, David
This work investigates the viability of using a cost effective, 623 nm light emitting diode (LED) based light source for high-speed schlieren imaging. The pulser circuit used to drive the LED was characterized on the basis of input response, pulse train characteristics, and pulse energies. Relative brightness data was measured with a photodiode and further examined within a schlieren system. Flow images of decaying, cylindrical shocks were obtained with the LED system and benchmarked against a high intensity discharge (HID) lamp. It was found that the LED could be overdriven up to 20 times the rated current while generating down to 100 ns pulses at up to a 1 MHz repetition rate. Moreover, although the LED system produced higher signals and reduced exposure times, similar image detail was observed for each light source. However, the LED exhibited a distinct advantage over the HID lamp in terms of image blur.
Open Access
Development of a Supersonic Reflected Shock Tunnel
(2017) Van Harberden, Wesley; Johansen, Craig; Ramirez-Serrano, Alex; Du, Ke; Langill, Phil
A reflected shock tunnel capable of producing supersonic/hypersonic flows was developed. The facility as a whole is described and tested for purposes of calibration and demonstration. A method for producing diaphragms in-lab was developed, and demonstrated to produce diaphragms with good bursting characteristics. The manufacture of diaphragms was also calibrated for the purpose of aiding in future experiments using the shock tunnel. The reflected shock tube portion was tested for its ability to generate a high pressure, high temperature, reservoir gas, as required for achieving supersonic flow by means of nozzle expansion. The nozzle itself was tested by means of inserting a wedge to create an oblique shock wave, and confirmed to successfully achieve supersonic flow. Finally, the entire shock tunnel was tested and confirmed to be capable of reproducing a given set of test conditions with a high level of repeatability.
Open Access
Development of an SUPG based numerical framework for the analysis of non-ionized hypersonic flows in thermochemical non-equilibrium
(2023-11-27) Codoni, David; Korobenko, Artem; Johansen, Craig; Mohamad, Abdulmajeed; Sudak, Leszek Jozef; Knudsen, David J; Hauke Bernardos, Guillermo
The present work focuses on the development of a numerical framework for the aerothermodynamic analysis in the hypersonic regime. In this work the Navier-Stokes equations for the compressible flows in thermochemical non-equilibrium are solved in the set of pressure-based primitive variables, using the Streamline-Upwind Petrov-Galerkin (SUPG) based stabilized formulation for the Finite Element Method (FEM) enhanced with a discontinuity-capturing operator. The first part of the project focuses on the validation of the fluid dynamic framework for compressible flows in high-speed regimes without considering real gas effects. In this part, the fluid is assumed ideal, non-reacting, and in thermal equilibrium. The numerical framework is validated against benchmark cases with increasing complexity, namely the flat plate, the compression corner, the two-dimensional cylinder and the three-dimensional atmospheric re-entry capsule. The results obtained gave the confidence that the SUPG stabilized formulation enhanced with a discontinuity-capturing term constitutes a valid approach to studying high-speed flows. The second part of the project involves the development and implementation of real gas effects at the hypersonic regime. The developed numerical framework is able to predict 5-species nonionized flows in thermochemical non-equilibrium. The numerical framework for reacting flows in thermal non-equilibrium is verified and validated against benchmark cases, such as the zero-dimensional nitrogen reactor, two-dimensional cylinder, and the three-dimensional hollow flare and double cone. Based on the good agreement of the results obtained with the available data in the literature, it is safe to state that the methodology presented in this work proved to be a valid alternative to analyse the non-ionized hypersonic flows in thermochemical non-equilibrium. The pressure-based primitive variables numerical framework presented in this work, set the first step towards the development of a Fluid-Thermal-Structure Interaction (FTSI) framework for the analysis of aerothermoelastic problems in the hypersonic regime.
Open Access
Development of Lattice-Augmented Fuels for Hybrid Rocket Applications
(2022-04-19) Hill, Colin; Johansen, Craig; Cantwell, Brian; Du, Ke; Mahnipey, Nader; Martinuzzi, Robert; Wood, David
Hybrid rocket propulsion systems, which utilize a solid fuel and liquid oxidizer, are among the safest and simplest rocket propulsion systems that can be developed. Despite these attractive qualities, the commercialization of the technology has been slow due to difficulties associated with scaling designs from lab-scale demonstration motors to functional propulsion systems for launch vehicles. The introduction of liquefying solid fuels, such as paraffin wax, have helped overcome some of the scaling issues traditionally associated with hybrid rockets, but a number of key challenges relating to combustion efficiency and the structural properties of wax-based fuels remain. The current work explores these challenges through the use of an additively-manufactured lattice embedded within the fuel grain. A novel process of generating three-dimensional gyroid surfaces with the desired properties has been developed that allows for lattices to be manufactured using fused deposition modeling (FDM) from a variety of thermoplastics. The application of lattice-augmented fuels to hybrid rocket systems at a number of scales is considered. An extensive series of tests were conducted on an optically accessible slab burner to characterize the regression characteristics of lattice augmented fuels. Lattice-augmented fuels were also demonstrated at a larger scale using a 4-kN nitrous oxide/paraffin hybrid rocket motor. Studies at this scale analyzed the regression rate of the fuel as well as methods of improving the combustion efficiency. A passive mixing device located in the combustion chamber was used to improve the combustion efficiency of the wax-based fuel by over 40%. Finally, lattice-augmented fuels were demonstrated in-flight during a series of sounding rocket flights which compared the performance of non-augmented to augmented fuels. The thesis has shown that the proposed strategy for improving wax-based fuels using lattice-augmentation performs well across a number of motor scales and can be successfully applied to an operational hybrid rocket system.